docs: def ToPhotlam(self, wave, flux, **kwargs):
          """Convert to ``photlam``.
  
          .. math::
  
              m = -0.4 \\; (\\textnormal{ST}_{\\lambda} + 21.1)
  
              \\textnormal{photlam} = \\frac{10^{m} \\lambda}{hc}
  
          where :math:`h` and :math:`c` are as defined in
          :ref:`pysynphot-constants`.
  
          Parameters
          ----------
          wave, flux : number or array_like
              Wavelength and flux values to be used for conversion.
  
          kwargs : dict
              Extra keywords (not used).
  
          Returns
          -------
          result : number or array_like
              Converted values.
  
          """
          return wave / H / C * 10.0**(-0.4 * (flux - STZERO))